Raster MTR improvements - part one (PR #3334)

doc/api_break.dox

@@ -414,6 +414,7 @@ be returned instead of a null pointer if no transformation is required.</li>
 <ul>
 <li>srcDataType() has been renamed to sourceDataType()</li>
 <li>srcInput() has been renamed to sourceInput()</li>
+<li>block() has new "feedback" argument.</li>
 </ul>
 
 \subsection qgis_api_break_3_0_QgsRelation QgsRelation

python/core/core.sip

@@ -54,6 +54,7 @@
 %Include qgsfeaturefilterprovider.sip
 %Include qgsfeatureiterator.sip
 %Include qgsfeaturerequest.sip
+%Include qgsfeedback.sip
 %Include qgsfield.sip
 %Include qgsgeometrysimplifier.sip
 %Include qgsgeometryvalidator.sip

python/core/qgsfeedback.sip

@@ -0,0 +1,43 @@
+
+/** \ingroup core
+ * Base class for feedback objects to be used for cancellation of something running in a worker thread.
+ * The class may be used as is or it may be subclassed for extended functionality
+ * for a particular operation (e.g. report progress or pass some data for preview).
+ *
+ * When cancel() is called, the internal code has two options to check for cancellation state:
+ * - if the worker thread uses an event loop (e.g. for network communication), the code can
+ *   make a queued connection to cancelled() signal and handle the cancellation in its slot.
+ * - if the worker thread does not use an event loop, it can poll isCancelled() method regularly
+ *   to see if the operation should be cancelled.
+ *
+ * The class is meant to be created and destroyed in the main thread.
+ *
+ * For map rendering, the object may be created in constructor of a QgsMapLayerRenderer
+ * subclass and available with QgsMapLayerRenderer::feedback() method. When a map rendering job
+ * gets cancelled, the cancel() method is called on the feedback object of all layers.
+ *
+ * @note added in QGIS 3.0
+ */
+class QgsFeedback : QObject
+{
+%TypeHeaderCode
+#include <qgsfeedback.h>
+%End
+
+  public:
+    //! Construct a feedback object
+    QgsFeedback( QObject* parent /TransferThis/ = nullptr );
+
+    virtual ~QgsFeedback();
+
+    //! Tells the internal routines that the current operation should be cancelled. This should be run by the main thread
+    void cancel();
+
+    //! Tells whether the operation has been cancelled already
+    bool isCancelled() const;
+
+  signals:
+    //! Internal routines can connect to this signal if they use event loop
+    void cancelled();
+
+};

python/core/qgsmaplayerrenderer.sip

@@ -12,6 +12,10 @@ class QgsMapLayerRenderer
     //! Do the rendering (based on data stored in the class)
     virtual bool render() = 0;
 
+    //! Access to feedback object of the layer renderer (may be null)
+    //! @note added in QGIS 3.0
+    virtual QgsFeedback* feedback() const;
+
     //! Return list of errors (problems) that happened during the rendering
     QStringList errors() const;
 

python/core/raster/qgsbrightnesscontrastfilter.sip

@@ -15,7 +15,7 @@ class QgsBrightnessContrastFilter : QgsRasterInterface
 
     bool setInput( QgsRasterInterface* input );
 
-    QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height );
+    QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) /Factory/;
 
     void setBrightness( int brightness );
     int brightness() const;

python/core/raster/qgshillshaderenderer.sip

@@ -31,7 +31,7 @@ class QgsHillshadeRenderer : QgsRasterRenderer
      */
     static QgsRasterRenderer* create( const QDomElement& elem, QgsRasterInterface* input ) /Factory/;
 
-    QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height ) /Factory/;
+    QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) /Factory/;
 
     void writeXml( QDomDocument& doc, QDomElement& parentElem ) const;
 

python/core/raster/qgshuesaturationfilter.sip

@@ -25,7 +25,7 @@ class QgsHueSaturationFilter : QgsRasterInterface
 
     bool setInput( QgsRasterInterface* input );
 
-    QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height );
+    QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) /Factory/;
 
     void setSaturation( int saturation );
     int saturation() const;

python/core/raster/qgsmultibandcolorrenderer.sip

@@ -12,7 +12,7 @@ class QgsMultiBandColorRenderer: QgsRasterRenderer
 
     static QgsRasterRenderer* create( const QDomElement& elem, QgsRasterDataProvider* provider ) /Factory/;
 
-    QgsRasterBlock* block( int bandNo, const QgsRectangle & extent, int width, int height ) /Factory/;
+    QgsRasterBlock* block( int bandNo, const QgsRectangle & extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) /Factory/;
 
     int redBand() const;
     void setRedBand( int band );

python/core/raster/qgspalettedrasterrenderer.sip

@@ -10,7 +10,7 @@ class QgsPalettedRasterRenderer : QgsRasterRenderer
     virtual QgsPalettedRasterRenderer * clone() const /Factory/;
     static QgsRasterRenderer* create( const QDomElement& elem, QgsRasterInterface* input ) /Factory/;
 
-    QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height ) /Factory/;
+    QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) /Factory/;
 
     /** Returns number of colors*/
     int nColors() const;

python/core/raster/qgsrasterdataprovider.sip

@@ -102,7 +102,7 @@ class QgsRasterDataProvider : QgsDataProvider, QgsRasterInterface
     virtual int ySize() const;
 
     /** Read block of data using given extent and size. */
-    virtual QgsRasterBlock *block( int theBandNo, const QgsRectangle &theExtent, int theWidth, int theHeight ) / Factory /;
+    virtual QgsRasterBlock *block( int theBandNo, const QgsRectangle &theExtent, int theWidth, int theHeight, QgsRasterBlockFeedback* feedback = nullptr ) / Factory /;
 
     /** Return true if source band has no data value */
     virtual bool sourceHasNoDataValue( int bandNo ) const;
@@ -306,7 +306,7 @@ class QgsRasterDataProvider : QgsDataProvider, QgsRasterInterface
     /** Read block of data using give extent and size
      * @note not available in python bindings
      */
-    //virtual void readBlock( int bandNo, QgsRectangle  const & viewExtent, int width, int height, void *data );
+    //virtual void readBlock( int bandNo, QgsRectangle  const & viewExtent, int width, int height, void *data, QgsRasterBlockFeedback* feedback = nullptr );
 
     /** Returns true if user no data contains value */
     bool userNoDataValuesContains( int bandNo, double value ) const;

python/core/raster/qgsrasterdrawer.sip

@@ -13,9 +13,9 @@ class QgsRasterDrawer
      * @param p destination QPainter
      * @param viewPort viewport to render
      * @param theQgsMapToPixel map to pixel convertor
-     * @param ctx render context
+     * @param feedback optional raster feedback object for cancellation/preview. Added in QGIS 3.0.
      */
-    void draw( QPainter* p, QgsRasterViewPort* viewPort, const QgsMapToPixel* theQgsMapToPixel, const QgsRenderContext *ctx = nullptr );
+    void draw( QPainter* p, QgsRasterViewPort* viewPort, const QgsMapToPixel* theQgsMapToPixel, QgsRasterBlockFeedback* feedback = nullptr );
 
   protected:
     /** Draws raster part

python/core/raster/qgsrasterinterface.sip

@@ -1,4 +1,18 @@
 
+/** \ingroup core
+ * Feedback object tailored for raster block reading.
+ *
+ * @note added in QGIS 3.0
+ */
+class QgsRasterBlockFeedback : QgsFeedback
+{
+%TypeHeaderCode
+#include <qgsrasterinterface.h>
+%End
+    // TODO: extend with preview functionality??
+};
+
+
 /** Base class for processing modules.
  *
  */
@@ -129,8 +143,9 @@ class QgsRasterInterface
      * @param extent extent of block
      * @param width pixel width of block
      * @param height pixel height of block
+     * @param feedback optional raster feedback object for cancellation/preview. Added in QGIS 3.0.
      */
-    virtual QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height ) = 0 /Factory/;
+    virtual QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) = 0 /Factory/;
 
     /** Set input.
       * Returns true if set correctly, false if cannot use that input */

python/core/raster/qgsrasteriterator.sip

@@ -12,8 +12,9 @@ class QgsRasterIterator
       @param nCols number of columns
       @param nRows number of rows
       @param extent area to read
+      @param feedback optional raster feedback object for cancellation/preview. Added in QGIS 3.0.
      */
-    void startRasterRead( int bandNumber, int nCols, int nRows, const QgsRectangle& extent );
+    void startRasterRead( int bandNumber, int nCols, int nRows, const QgsRectangle& extent, QgsRasterBlockFeedback* feedback = nullptr );
 
     /** Fetches next part of raster data, caller takes ownership of the block and
        caller should delete the block.

python/core/raster/qgsrasternuller.sip

@@ -19,7 +19,7 @@ class QgsRasterNuller : QgsRasterInterface
 
     Qgis::DataType dataType( int bandNo ) const;
 
-    QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height ) / Factory /;
+    QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) / Factory /;
 
     void setNoData( int bandNo, const QgsRasterRangeList& noData );
 

python/core/raster/qgsrasterprojector.sip

@@ -74,7 +74,7 @@ class QgsRasterProjector : QgsRasterInterface
     // Translated precision mode, for use in ComboBox etc.
     static QString precisionLabel( Precision precision );
 
-    QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height ) / Factory /;
+    QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) / Factory /;
 
     /** Calculate destination extent and size from source extent and size */
     bool destExtentSize( const QgsRectangle& theSrcExtent, int theSrcXSize, int theSrcYSize,

python/core/raster/qgsrasterrenderer.sip

@@ -38,7 +38,7 @@ class QgsRasterRenderer : QgsRasterInterface
 
     virtual bool setInput( QgsRasterInterface* input );
 
-    virtual QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height ) = 0 / Factory /;
+    virtual QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) = 0 / Factory /;
 
     bool usesTransparency() const;
 

python/core/raster/qgsrasterresamplefilter.sip

@@ -19,7 +19,7 @@ class QgsRasterResampleFilter : QgsRasterInterface
 
     bool setInput( QgsRasterInterface* input );
 
-    QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height ) /Factory/;
+    QgsRasterBlock *block( int bandNo, const QgsRectangle &extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) /Factory/;
 
     /** Set resampler for zoomed in scales. Takes ownership of the object*/
     void setZoomedInResampler( QgsRasterResampler* r /Transfer/ );

python/core/raster/qgssinglebandcolordatarenderer.sip

@@ -12,7 +12,7 @@ class QgsSingleBandColorDataRenderer: QgsRasterRenderer
 
     bool setInput( QgsRasterInterface* input );
 
-    QgsRasterBlock* block( int bandNo, const QgsRectangle & extent, int width, int height ) / Factory /;
+    QgsRasterBlock* block( int bandNo, const QgsRectangle & extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) / Factory /;
 
     void writeXml( QDomDocument& doc, QDomElement& parentElem ) const;
 

python/core/raster/qgssinglebandgrayrenderer.sip

@@ -16,7 +16,7 @@ class QgsSingleBandGrayRenderer: QgsRasterRenderer
 
     static QgsRasterRenderer* create( const QDomElement& elem, QgsRasterDataProvider* provider ) /Factory/;
 
-    QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height ) / Factory /;
+    QgsRasterBlock *block( int bandNo, const QgsRectangle & extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) / Factory /;
 
     int grayBand() const;
     void setGrayBand( int band );

python/core/raster/qgssinglebandpseudocolorrenderer.sip

@@ -11,7 +11,7 @@ class QgsSingleBandPseudoColorRenderer: QgsRasterRenderer
 
     static QgsRasterRenderer* create( const QDomElement& elem, QgsRasterDataProvider* provider ) /Factory/;
 
-    QgsRasterBlock* block( int bandNo, const QgsRectangle & extent, int width, int height ) / Factory /;
+    QgsRasterBlock* block( int bandNo, const QgsRectangle & extent, int width, int height, QgsRasterBlockFeedback* feedback = nullptr ) / Factory /;
 
     /** Takes ownership of the shader*/
     void setShader( QgsRasterShader* shader /Transfer/ );

src/app/main.cpp

@@ -194,6 +194,14 @@ static void dumpBacktrace( unsigned int depth )
     depth = 20;
 
 #if ((defined(linux) || defined(__linux__)) && !defined(ANDROID)) || defined(__FreeBSD__)
+  // Below there is a bunch of operations that are not safe in multi-threaded
+  // environment (dup()+close() combo, wait(), juggling with file descriptors).
+  // Maybe some problems could be resolved with dup2() and waitpid(), but it seems
+  // that if the operations on descriptors are not serialized, things will get nasty.
+  // That's why there's this lovely mutex here...
+  static QMutex mutex;
+  QMutexLocker locker( &mutex );
+
   int stderr_fd = -1;
   if ( access( "/usr/bin/c++filt", X_OK ) < 0 )
   {

src/core/CMakeLists.txt

@@ -456,6 +456,7 @@ SET(QGIS_CORE_MOC_HDRS
   qgsdataprovider.h
   qgsdbfilterproxymodel.h
   qgseditformconfig.h
+  qgsfeedback.h
   qgsgeometryvalidator.h
   qgsgml.h
   qgsgmlschema.h

src/core/qgsfeedback.h

@@ -0,0 +1,73 @@
+/***************************************************************************
+  qgsfeedback.h
+  --------------------------------------
+  Date                 : July 2016
+  Copyright            : (C) 2016 by Martin Dobias
+  Email                : wonder dot sk at gmail dot com
+ ***************************************************************************
+ *                                                                         *
+ *   This program is free software; you can redistribute it and/or modify  *
+ *   it under the terms of the GNU General Public License as published by  *
+ *   the Free Software Foundation; either version 2 of the License, or     *
+ *   (at your option) any later version.                                   *
+ *                                                                         *
+ ***************************************************************************/
+
+#ifndef QGSFEEDBACK_H
+#define QGSFEEDBACK_H
+
+#include <QObject>
+
+/** \ingroup core
+ * Base class for feedback objects to be used for cancellation of something running in a worker thread.
+ * The class may be used as is or it may be subclassed for extended functionality
+ * for a particular operation (e.g. report progress or pass some data for preview).
+ *
+ * When cancel() is called, the internal code has two options to check for cancellation state:
+ * - if the worker thread uses an event loop (e.g. for network communication), the code can
+ *   make a queued connection to cancelled() signal and handle the cancellation in its slot.
+ * - if the worker thread does not use an event loop, it can poll isCancelled() method regularly
+ *   to see if the operation should be cancelled.
+ *
+ * The class is meant to be created and destroyed in the main thread.
+ *
+ * For map rendering, the object may be created in constructor of a QgsMapLayerRenderer
+ * subclass and available with QgsMapLayerRenderer::feedback() method. When a map rendering job
+ * gets cancelled, the cancel() method is called on the feedback object of all layers.
+ *
+ * @note added in QGIS 3.0
+ */
+class CORE_EXPORT QgsFeedback : public QObject
+{
+    Q_OBJECT
+  public:
+    //! Construct a feedback object
+    QgsFeedback( QObject* parent = nullptr )
+        : QObject( parent )
+        , mCancelled( false )
+    {}
+
+    virtual ~QgsFeedback() {}
+
+    //! Tells the internal routines that the current operation should be cancelled. This should be run by the main thread
+    void cancel()
+    {
+      if ( mCancelled )
+        return;  // only emit the signal once
+      mCancelled = true;
+      emit cancelled();
+    }
+
+    //! Tells whether the operation has been cancelled already
+    bool isCancelled() const { return mCancelled; }
+
+  signals:
+    //! Internal routines can connect to this signal if they use event loop
+    void cancelled();
+
+  private:
+    //! Whether the operation has been cancelled already. False by default.
+    bool mCancelled;
+};
+
+#endif // QGSFEEDBACK_H

src/core/qgsmaplayerrenderer.h

@@ -18,6 +18,8 @@
 
 #include <QStringList>
 
+class QgsFeedback;
+
 /** \ingroup core
  * Base class for utility classes that encapsulate information necessary
  * for rendering of map layers. The rendering is typically done in a background
@@ -49,6 +51,10 @@ class CORE_EXPORT QgsMapLayerRenderer
     //! Do the rendering (based on data stored in the class)
     virtual bool render() = 0;
 
+    //! Access to feedback object of the layer renderer (may be null)
+    //! @note added in QGIS 3.0
+    virtual QgsFeedback* feedback() const { return nullptr; }
+
     //! Return list of errors (problems) that happened during the rendering
     QStringList errors() const { return mErrors; }
 

src/core/qgsmaprenderercustompainterjob.cpp

@@ -15,6 +15,7 @@
 
 #include "qgsmaprenderercustompainterjob.h"
 
+#include "qgsfeedback.h"
 #include "qgslabelingenginev2.h"
 #include "qgslogger.h"
 #include "qgsmaplayerregistry.h"
@@ -124,6 +125,8 @@ void QgsMapRendererCustomPainterJob::cancel()
   for ( LayerRenderJobs::iterator it = mLayerJobs.begin(); it != mLayerJobs.end(); ++it )
   {
     it->context.setRenderingStopped( true );
+    if ( it->renderer->feedback() )
+      it->renderer->feedback()->cancel();
   }
 
   QTime t;